Canvas How to - Overlap shapes with transparent color

Question

We would like to know how to overlap shapes with transparent color.

Answer


<!--from w ww  .  ja  va  2  s . c  o  m-->
<html>
    <head>
        <script>
            window.onload = function(){
                var canvas = document.getElementById("myCanvas");
                var context = canvas.getContext("2d");
                
                // draw rectangle
                context.beginPath();
                context.rect(240, 30, 130, 130);
                context.fillStyle = "blue";
                context.fill();
                
                // draw circle
                context.globalAlpha = 0.5; // set global alpha
                context.beginPath();
                context.arc(359, 150, 70, 0, 2 * Math.PI, false);
                context.fillStyle = "red";
                context.fill();
            };
        </script>
    </head>
    <body>
        <canvas id="myCanvas" width="600" height="250" style="border:1px solid black;">
        </canvas>
    </body>
</html>

The code above is rendered as follows: